The adequate measurement of information system project success is yet an unsolved problem. By means of a qualitative empirical study, we analyze the way companies in Germany measure the success of their information system projects. We conducted 9 semi-structured expert interviews with project managers and other decision-makers to gather information about (1) their subjective views on and (2) their companies’ actual measurement of information system project success. Although the participants consider further success dimensions as important, the companies almost exclusively rely on the traditional criteria of time, cost, and quality. Furthermore, we provide insights into reasons for this behaviour. Practitioners assume that a project is efficient when it is completed on-time and inbudget as long as plans are not exceeded. Our study provides a new perspective on information system project success and shows that it is mainly a matter of measurability to use further success dimensions.